Method for in situ extraction of hydrocarbon materials

ABSTRACT

A method for in situ extraction of hydrocarbon materials in a subsurface region includes increasing permeability of a low permeability hydrocarbon-containing subsurface region to create a first well sub-region and a second well sub-region vertically below the first well sub-region. The first well sub-region is heated to extract liquid hydrocarbon materials that flow to the second well sub-region. The liquid hydrocarbon materials are then transported from the second well sub-region.

BACKGROUND

This disclosure relates to methods of extracting hydrocarbon materials from subterranean geological formations.

As energy consumption rises, alternative sources of oil to traditional oil wells are developed to meet consumption demand. For instance, one alternative oil source is oil shale. The oil shale is removed from subterranean geological formations and then processed at the surface to extract the oil from the rock. The extracted oil is subsequently refined using conventional refining techniques.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example method for in situ extraction of hydrocarbon materials in a subsurface region.

FIG. 2 illustrates an example well arrangement for carrying out a method for in situ extraction of hydrocarbon materials in a subsurface region.

DETAILED DESCRIPTION

FIG. 1 illustrates an example method 20 for in situ extraction of hydrocarbon materials in a subsurface region. As will be described, the exemplary method 20 may be used to extract and recover hydrocarbon materials from impermeable or low permeability subsurface regions that contain oil shale deposits or other similar geologic formations that include oil or kerogen. In some examples, the deposits are consolidated carbonates having oil, heavy oil or bitumen and/or consolidated oil sands having oil, heavy oil or bitumen. As will also be described in further detail, the disclosed method 20 utilizes a technique of heating the subsurface region to extract useful hydrocarbon materials in situ and subsequently move the extracted hydrocarbon materials to the surface, without the need for removing bulk oil-containing rock.

In the illustrated example, the method 20 generally includes steps 22, 24 and 26, although it is to be understood that each of the steps 22, 24 and 26 may include any number of sub-steps in order to carry out or facilitate the primary steps 22, 24 or 26. In the example shown, step 22 includes the action increasing permeability of a low permeability hydrocarbon-containing subsurface region. The increase in permeability creates a plurality of well sub-regions that include a first well sub-region and a second well sub-region that is located vertically below the first well sub-region. The second step 24 includes the action of heating the first well sub-region to extract liquid hydrocarbon materials that then gravimetrically flow from the first well sub-region to the second well sub-region. The third step 26 includes the action of transporting the liquid hydrocarbon materials from the second well sub-region to the surface, for example.

The method 20 will be further described with reference to FIG. 2, which shows an example well arrangement 40 for carrying out the method 20. It is to be understood that the disclosed well arrangement 40 is only an example and that the well arrangement 40 can be varied in accordance with the method 20.

In the illustrated example, the well arrangement 40 is configured relative to a surface region 42 and a subsurface region 44. The subsurface region 44 includes a low permeability hydrocarbon-containing subsurface region 44 a that is generally located between a near subsurface region 44 b and a far subsurface region 44 c. That is, the low permeability hydrocarbon-containing subsurface region 44 a is at a depth that is between the near subsurface region 44 b and the far subsurface region 44 c. In some examples, the subsurface region 44 a is at a depth of 500 to several thousands of feet.

In this example, three well sub-regions 46 a, 46 b and 46 c are created within the low permeability hydrocarbon-containing subsurface region 44 a by increasing the permeability of the subsurface region 44 a. For instance, each of the well sub-regions 46 a, 46 b and 46 c are created by rubblizing the subsurface region 44 a. The subsurface region 44 a is rubblized using horizontal well strings, hydraulic fracturing and/or by using a compressed gas or supercritical gas. The rock fractures to form a rubble bed of broken rock, which increases the flow area for the hot working fluid, increases the rock surface area for heat transfer, and reduces the size of the rock dimension or diameter for affecting diffusion and expulsion of the liquid oil from the rock pores. In general, techniques of rubblizing are known and, given this description, one of ordinary skill in the art will recognize suitable rubblizing techniques to meet their particular needs.

As shown, the first well sub-region 46 a is fluidly connected to the surface region 42 by injection duct 48 a, the second well sub-region 46 b is connected to the surface region 42 by collection duct 48 b, and the third well sub-region 46 c is fluidly connected with the surface region 42 by vent duct 48 c. In that regard, the first well sub-region 46 a is considered to be an injection well sub-region, the second well sub-region 46 b is considered to be a collection well sub-region and the third well sub-region 46 c is considered to be a vent well sub-region. In the illustrated example, the injection well sub-region and the vent well sub-region are at substantially equivalent subsurface depths.

The injection duct 48 a and the vent duct 48 c are connected by a surface battery 50 to recirculate a working fluid through the subsurface region 44 a. In the illustrated example, the surface battery 50 includes a condenser 52, a turbo-compressor 54, a separator 56 and a gas source 58.

A downhole combustion heater 60 is located within the injection duct 48 a below the surface region 42. The combustion heater 60 is located in close proximity to the first well sub-region 46 a for enhancement of thermal efficiency in conveying heated working fluid into the first well sub-region 46 a. The close proximity allows for the efficient generation and transport of the heat without suffering heat losses in the long transport of the working fluid from a remote surface heating facility. An additoinal benefit of the close proximity is where the subsurface region 44 a is very deep, under a body of water, under permafrost, or a combination of these conditions.

The downhole combustion heater 60 operates to heat the rubblized material within the first well sub-region 46 a to extract hydrocarbon-containing materials from the oil shale or other oil-bearing material. The combustion heater 60 distributes the heated working fluid into the first well sub-region 46 a to slowly heats the shale and release (i.e., by the process of catagenesis) liquid oil. The heating profile with regard to time and temperature can be adjusted such that catagenesis of the kerogen to oil or oil and gas products is controlled.

In one example, the combustion heater 60 is used to heat the first well sub-region 46 a to a temperature of 350°-450° C. (662°-842° F. In a further example, the target heating temperature is approximately 350° C.-400° C. (698° F.-752° F.). The given temperature range thermally decomposes kerogen to a light, low viscosity liquid oil by very slowly heating the first well sub-region 46 a. In comparison, surface retorting of mined rock is conducted at much higher temperatures for much shorter times.

In one example, the combustion heater 60 is a vitiated, pressurized combustor unit that is designed for high thermal output, such as a combustor that is of similar design to a gas or liquid fueled rocket engine.

Depending on the type of oil-bearing material in the subsurface region, the extracted hydrocarbon-containing materials are liquid hydrocarbon material, gaseous hydrocarbon material or both. The extracted liquid hydrocarbon material flows downwards into the second well sub-region 46 b, where it subsequently transported through collection duct 48 b to the surface region 42.

After initial heating of the first well sub-region 46 a to extract and drain liquid hydrocarbon material, the temperature in the first well sub-region 46 a is optionally slowly increased to more efficiently release hydrocarbon gases and condensable liquids and to produce additional liquid oil by the thermal decomposition of any residual bitumen products. In one example, fuel gases that are extracted are used to fuel the combustion heater 60.

The working fluid that is heated and provided into the first well sub-region 46 a is a non-degrading fluid, such as carbon dioxide, methane, nitrogen or mixtures thereof. That is, the working fluid does not decompose into other shorter chain molecules that can otherwise foul the surfaces of the combustion heater 60 or the pores within the wells. In a further example, the working fluid is a compressed gas or supercritical gas.

The heated working fluid provided from the turbo-compressor 54 to the combustion heater 60 and into the first well sub-region 46 a circulates to the third well sub-region 46 c. The extracted gaseous hydrocarbon materials are carried with the working fluid into the third well sub-region 46 c and are vented through the vent duct 48 c to the surface region 42.

The condenser 52 condenses any condensable hydrocarbon materials within the vented gas and the separator 56 subsequently separates the condensed fluids, such as liquid oils and water. The remaining gaseous material is made up substantially of the working fluid, which is then conveyed to the compressor 54 for recirculation through the combustion heater 60 into the first well sub-region 46 a. A combustible gas, such as oxygen, is provided from the gas source 58 into the injection duct 48 a for combustion in the combustion heater 60.

Experimental modeling of the method 20 using the disclosed working fluids suggests that the well can be heated to the desired temperature and oil released from the rock over a reasonable period of field production life (e.g., 10-15 years). In some examples, the parameters that influence the production rate are thermal losses within the formation and within the length of the injection ducts (minimized by the downhole combustion heater 60), volumetric rate of circulation of the heated working fluid, temperature of the injected working fluid, and the geometric character of the rubblized rock.

Although a combination of features is shown in the illustrated examples, not all of them need to be combined to realize the benefits of various embodiments of this disclosure. In other words, a system designed according to an embodiment of this disclosure will not necessarily include all of the features shown in any one of the Figures or all of the portions schematically shown in the Figures. Moreover, selected features of one example embodiment may be combined with selected features of other example embodiments.

The preceding description is exemplary rather than limiting in nature. Variations and modifications to the disclosed examples may become apparent to those skilled in the art that do not necessarily depart from the essence of this disclosure. The scope of legal protection given to this disclosure can only be determined by studying the following claims. 

1. A method for in-situ extraction of hydrocarbon materials in a subsurface region, the method comprising: increasing permeability of a low permeability hydrocarbon-containing subsurface region to create a plurality of well sub-regions that include a first well sub-region and a second well sub-region vertically below the first well sub-region; heating the first well sub-region to extract liquid hydrocarbon materials that flow from the first well sub-region to the second well sub-region; and transporting the liquid hydrocarbon materials from the second well sub-region.
 2. The method as recited in claim 1, including increasing the permeability by rubblizing the subsurface region.
 3. The method as recited in claim 1, wherein the first well sub-region and the second well sub-region are fluidly connected.
 4. The method as recited in claim 1, including heating by using a downhole combustion heater.
 5. The method as recited in claim 1, including heating the first well sub-region to a temperature of 350°-450° C. (662°-842° F.).
 6. The method as recited in claim 1, including heating by injecting a heated working fluid into the first well sub-region.
 7. The method as recited in claim 6, including transporting the working fluid from the first well sub-region, purifying the working fluid and recirculating the working fluid back into the first well sub-region.
 8. The method as recited in claim 6, wherein the working fluid is selected from a group consisting of carbon dioxide, methane, nitrogen and combinations thereof.
 9. The method as recited in claim 1, including increasing the permeability to also create a third well sub-region above the second well sub-region, wherein the heating of the first well sub-region causes the extraction of gaseous hydrocarbon material that flows from the first well sub-region to the third well sub-region, and transporting the gaseous hydrocarbon material from the third well sub-region.
 10. The method as recited in claim 9, including circulating a heated working fluid from the first well sub-region to the third well sub-region.
 11. The method as recited in claim 1, wherein the subsurface region includes oil shale having kerogen.
 12. A method for in-situ extraction of hydrocarbon materials in a subsurface region, the method comprising: increasing permeability of a low permeability hydrocarbon-containing subsurface region to create an injection well sub-region, a vent well sub-region and a collection well sub-region that is vertically below the injection well sub-region; heating the injection well sub-region to extract gaseous hydrocarbon materials and liquid hydrocarbon materials, where the liquid hydrocarbon materials flow from the injection well sub-region to the collection well sub-region and the gaseous hydrocarbon materials flow to the vent well sub-region; and transporting the liquid hydrocarbon materials from the collection well sub-region and the gaseous hydrocarbon materials from the vent well sub-region.
 13. The method as recited in claim 12, including heating by using a downhole combustion heater.
 14. The method as recited in claim 12, including heating the injection well sub-region to a temperature of 350°-450° C. (662°-842° F.).
 15. The method as recited in claim 12, including heating by injecting a heated working fluid into the injection well sub-region.
 16. The method as recited in claim 12, wherein the injection well sub-region, the collection well sub-region and the vent well sub-region are all fluidly connected together.
 17. The method as recited in claim 12, wherein the injection well sub-region and the vent well sub-region are at substantially equivalent subsurface depths.
 18. A well arrangement for in-situ extraction of hydrocarbon materials in a subsurface region, the well arrangement comprising: an injection duct extending subsurface into a first well sub-region; a collection duct extending subsurface from a second well sub-region that is fluidly connected with the first well sub-region; a vent duct extending subsurface from a third well sub-region that is fluidly connected with the first well sub-region and the second well sub-region; a surface battery connecting the vent duct and the injection duct; and a downhole heater in the injection duct.
 19. The well arrangement as recited in claim 18, wherein the surface battery includes a turbo-compressor, a separator and a condenser.
 20. The well arrangement as recited in claim 18, wherein the collection duct extends to a deeper depth than the injector duct and the vent duct. 